Definition of "Sour" :

noun: the property of being acidic

noun: the taste experience when vinegar or lemon juice is taken into the mouth

noun: a cocktail made of a liquor (especially whiskey or gin) mixed with lemon or lime juice and sugar

verb: go sour or spoil

"The milk has soured."

verb: make sour or more sour

adjective: smelling of fermentation or staleness

adjective: showing a brooding ill humor

"A sour temper."

adjective: inaccurate in pitch

"A false (or sour) note."

adjective: having a sharp biting taste

adjective: in an unpalatable state

"Sour milk."

adjective: one of the four basic taste sensations; like the taste of vinegar or lemons